Multiple transducer delivery device and method

ABSTRACT

A stenotic lesion can be characterized by measuring both pressure drop across the stenotic lesion and the size of the vessel lumen adjacent the stenotic lesion, both with sensors delivered intravascularly to the stenotic lesion site. The size (e.g., inner diameter, cross-sectional profile) of the vessel lumen adjacent the stenotic lesion can be measured via one or more intravascular ultrasound transducers. Such one or more intravascular ultrasound transducer(s) can be delivered to the site of the stenotic lesion with the same delivery device that carries a pressure transducer.

TECHNICAL FIELD

This disclosure relates to methods and devices for assessing theseverity of a stenotic lesion in a patient's vasculature.

BACKGROUND

Assessing the severity of a stenotic lesion is an important part ofrecommending a treatment option. In some instances, if the stenoticlesion is permitted to grow unchecked, it can lead to a blockage ofblood flow which can cause a variety of very significant problems.Common treatment options, such as a stent, angioplasty, etc. are oftenrecommended to inhibit or roll back growth of a stenotic lesion. Thatsaid, treatment options can result in their own negative consequences.Thus, if the characteristics of the stenotic lesion are such that theyhave a minimal impact on the flow of blood through the vessel, it may berecommended to monitor the stenotic lesion over time but take nointervening action other than to administer drug therapy. Angiograms arecommon methods of assessing the severity of a stenotic lesion, but, inmany cases, there is a desire for additional means of gatheringinformation to more fully characterize the stenotic lesion.

SUMMARY

Embodiments of the present invention allow more full characterization ofa stenotic lesion by measuring both pressure drop across the stenoticlesion and the size of the vessel lumen adjacent the stenotic lesion,both with sensors delivered intravascularly to the stenotic lesion site.In preferred embodiments, the size (e.g., inner diameter,cross-sectional profile) of the vessel lumen adjacent the stenoticlesion can be measured via one or more intravascular ultrasoundtransducers. In preferred embodiments, the intravascular ultrasoundtransducer(s) can be delivered to the site of the stenotic lesion withthe same delivery device that carries the pressure transducer(s).

In some embodiments, an intravascular transducer delivery device for usewith a patient is provided. The intravascular transducer delivery devicecan include a distal sleeve, which can have a guidewire lumen forslidably receiving a medical guidewire. The intravascular transducerdelivery device can include a proximal portion that may be coupled tothe distal sleeve. The intravascular transducer delivery device caninclude a first pressure transducer, which can be coupled to the distalsleeve and/or the proximal portion. The first pressure transducer may beadapted to take a first intravascular fluid pressure measurement andgenerate a first pressure signal representative of the firstintravascular fluid pressure measurement. The intravascular transducerdelivery device may include a first pressure transducer conductor incommunication with the first pressure transducer. The first pressuretransducer conductor may be adapted to communicate the first pressuresignal outside of the patient through the proximal portion. Theintravascular transducer delivery device may include a first ultrasoundtransducer, which can be coupled to the distal sleeve and/or theproximal portion. The first ultrasound transducer may be adapted to takea first intravascular physical dimension measurement and generate afirst ultrasound signal representative of the first intravascularphysical dimension measurement. The intravascular transducer deliverydevice may include a first ultrasound transducer conductor incommunication with the first ultrasound transducer. The first ultrasoundtransducer conductor can be adapted to communicate the first ultrasoundsignal outside of the patient through the proximal portion.

Some embodiments of the intravascular transducer delivery device mayhave one or more of the following features. In some embodiments, thefirst pressure transducer may be a fiber optic pressure transducer. Someembodiments may include a second pressure transducer coupled to thedistal sleeve and/or the proximal portion. In some such embodiments, thesecond pressure transducer can be adapted to take a second intravascularfluid pressure measurement and generate a second pressure signalrepresentative of the second intravascular fluid pressure measurement.In some such embodiments, the second pressure transducer may be spacedaxially in the vessel lumen from the first pressure transducer by adistance that corresponds to a stenotic lesion. In some embodiments, thefirst pressure transducer can be coupled to the distal sleeve. In someembodiments, the first ultrasound transducer may include an ultrasoundtransducer ring. In some embodiments, the first ultrasound transducercan be coupled to the distal sleeve. In some embodiments, the firstultrasound transducer may be positioned distal to the first pressuretransducer. In some embodiments, the first intravascular physicaldimension measurement can include a radial distance from the firstultrasound transducer to a vessel wall.

Some embodiments of the intravascular transducer delivery device mayinclude a second ultrasound transducer and/or a third ultrasoundtransducer, both coupled to the distal sleeve and/or the proximalportion. In such embodiments, the second ultrasound transducer can beadapted to take a second intravascular physical dimension measurementand generate a second ultrasound signal representative of the secondintravascular physical dimension measurement. In such embodiments, thethird ultrasound transducer can be adapted to take a third intravascularphysical dimension measurement and generate a third ultrasound signalrepresentative of the third intravascular physical dimensionmeasurement. In such embodiments, the first ultrasound transducer, thesecond ultrasound transducer, and the third ultrasound transducer may bespaced about a circumference of the distal sleeve and/or the proximalportion approximately 120° from one another. In some such embodiments,the first ultrasound transducer conductor may in communication with thesecond ultrasound transducer and the third ultrasound transducer. Insome such embodiments, the first ultrasound transducer conductor may beadapted to communicate the second ultrasound signal and the thirdultrasound signal outside of the patient through the proximal portion.In some embodiments, the intravascular transducer delivery device mayinclude a second ultrasound transducer conductor in communication withthe second ultrasound transducer. In some such embodiments, the secondultrasound transducer conductor may be adapted to communicate the secondultrasound signal outside of the patient through the proximal portion.In some embodiments, the intravascular transducer delivery device mayinclude a third ultrasound transducer conductor in communication withthe third ultrasound transducer. In some such embodiments, the thirdultrasound transducer conductor may be adapted to communicate the thirdultrasound signal outside of the patient through the proximal portion.

In some embodiments, a method of gathering information about a stenoticlesion is provided. Some embodiments involve sliding an intravasculartransducer delivery device over a medical guidewire to position a firstpressure transducer and a first ultrasound transducer near the stenoticlesion. Some embodiments involve taking a first intravascular fluidpressure measurement near the stenotic lesion with the first pressuretransducer. Some embodiments involve taking a first intravascularphysical dimension measurement near the stenotic lesion with the firstultrasound transducer. Some preferred embodiments involve taking thefirst intravascular fluid pressure measurement and the firstintravascular physical dimension measurement contemporaneously (e.g.,close enough together in time to preclude (a) positioning a pressuretransducer near the stenotic lesion, (b) taking the intravascular fluidpressure measurement (commonly under hyperemic conditions), (c)withdrawing the pressure transducer from the patient's body, (d)inserting an ultrasound transducer into the patient's body, (e)positioning the ultrasound transducer near the stenotic lesion, and (f)taking the intravascular physical dimension measurement). In someembodiments, the first intravascular fluid pressure measurement and thefirst intravascular physical dimension measurement may be taken, e.g.,within two minutes, one and a half minutes, one minute, 50 seconds, 40seconds, 30 seconds, 20 seconds, or 10 seconds of one another.

Some embodiments of the method of gathering information about a stenoticlesion may have one or more of the following features. In someembodiments, the first intravascular fluid pressure measurement may betaken from a location distal to the stenotic lesion. In someembodiments, the method can further include using the firstintravascular fluid pressure measurement to assess pressure drop acrossthe stenotic lesion. In some such embodiments, assessing pressure dropacross the stenotic lesion may include calculating FFR or iFR. In someembodiments, the method may further include using the firstintravascular physical dimension measurement to calculate a diameter orcross-sectional profile of the vessel lumen adjacent the stenotic lesionand/or using the first intravascular fluid pressure measurement toassess pressure drop across the stenotic lesion. In some embodiments,the method may further include taking (e.g., contemporaneously) a secondintravascular physical dimension measurement near the stenotic lesionwith the first ultrasound transducer. In some such embodiments, thesecond intravascular physical dimension measurement may be taken from asecond location that is axially spaced in the vessel lumen from a firstlocation at which the first intravascular physical dimension measurementis taken. In some embodiments, the method may further include using thefirst intravascular physical dimension measurement to calculate a firstdiameter or a first cross-sectional profile of the vessel lumen at thefirst location. In some embodiments, the method may further includeusing the second intravascular physical dimension measurement tocalculate a second diameter or a second cross-sectional profile of thevessel lumen at the second location. In some such embodiments, an axialprofile of the vessel lumen's diameter and/or cross-sectional areaadjacent the stenotic lesion may be taken. In some embodiments, themethod may further include displaying information regarding pressuredrop across the stenotic lesion based on the first intravascular fluidpressure measurement. In some embodiments, the method may furtherinclude displaying information regarding a diameter or cross-sectionalprofile of the vessel lumen adjacent the stenotic lesion based on thefirst intravascular physical dimension measurement. In some preferredembodiments, the displaying may be on an injection system control panel.In some embodiments, the method may further include withdrawing theintravascular transducer delivery device over the medical guidewirewithout withdrawing the medical guidewire. In some embodiments, themethod may further include deploying an interventional therapy device tothe stenotic lesion using the same medical guidewire.

In some embodiments, one or more additional transducers may bepositioned near the stenotic lesion. In some embodiments, sliding theintravascular transducer delivery device over the medical guidewire mayfurther position a second pressure transducer near the stenotic lesion.In some such embodiments, the method may further include taking a secondintravascular fluid pressure measurement near the stenotic lesion withthe second pressure transducer. In some preferred embodiments, thesecond intravascular fluid pressure measurement may be contemporaneouswith the first intravascular fluid pressure measurement and the firstintravascular physical dimension measurement. In some embodiments, thefirst intravascular fluid pressure measurement may be taken from a firstlocation that is distal to the stenotic lesion. In some embodiments, thesecond intravascular fluid pressure measurement may be taken from asecond location that is proximal to the stenotic lesion. In someembodiments, the method may further include using the firstintravascular fluid pressure measurement and the second intravascularfluid pressure measurement to assess pressure drop across the stenoticlesion. In some embodiments, sliding the intravascular transducerdelivery device over the medical guidewire may further position a secondultrasound transducer and a third ultrasound transducer near thestenotic lesion. In some embodiments, the method may further includetaking a second intravascular physical dimension measurement near thestenotic lesion with the second ultrasound transducer and a thirdintravascular physical dimension measurement near the stenotic lesionwith the third ultrasound transducer. In some preferred embodiments, thesecond intravascular physical dimension measurement and the thirdintravascular physical dimension measurement are taken contemporaneouslywith each other and with the first intravascular fluid pressuremeasurement and the first intravascular physical dimension measurement.In some embodiments, the method may further include using the firstintravascular physical dimension measurement, the second intravascularphysical dimension measurement, and the third intravascular physicaldimension measurement to calculate a diameter or cross-sectional profileof the vessel lumen adjacent the stenotic lesion.

In some embodiments, a fluid injection system is provided. The fluidinjection system can include fluid tubing adapted to provide fluidcommunication between the fluid injection system and a patient. Thefluid injection system can include a processor adapted to receive afirst pressure signal representative of a first intravascular fluidpressure measurement taken near a stenotic lesion of the patient. Insome embodiments, the processor can be adapted to receive a firstultrasound signal representative of a first intravascular physicaldimension measurement taken near the stenotic lesion. In someembodiments, the processor may be adapted to receive the first pressuresignal and the first ultrasound signal contemporaneously (e.g., withintwo minutes, one and a half minutes, one minute, 50 seconds, 40 seconds,30 seconds, 20 seconds, or 10 seconds of one another). Some fluidinjection systems may include a control panel. The control panel may beadapted to receive from the processor a first set of pressureinformation based on the first intravascular fluid pressure measurementand/or a first set of ultrasound information based the firstintravascular physical dimension measurement. The control panel may beadapted to display the first set of pressure information and the firstset of ultrasound information.

Some embodiments of the fluid injection system may have one or more ofthe following features. In some embodiments, the first intravascularfluid pressure measurement may be taken from a location distal to thestenotic lesion. In some embodiments, the first set of pressureinformation may include information regarding pressure drop across thestenotic lesion. In some instances, the first set of pressureinformation may include FFR or iFR. In some embodiments, the first setof ultrasound information may include information regarding a diameteror cross-sectional profile of the stenotic lesion and/or the first setof pressure information can include information regarding pressure dropacross the stenotic lesion.

In some embodiments, the processor may be further adapted to receiveadditional signals. In some embodiments, the processor may be furtheradapted to receive a second pressure signal representative of a secondintravascular fluid pressure measurement taken near the stenotic lesion.In some preferred embodiments, the processor may be adapted to receivethe second pressure signal contemporaneously with the first pressuresignal and the first ultrasound signal. In some embodiments, the firstset of pressure information may be based on the first intravascularfluid pressure measurement and the second intravascular fluid pressuremeasurement. In some embodiments, the first intravascular fluid pressuremeasurement may be taken from a first location that is distal to thestenotic lesion, and the second intravascular fluid pressure measurementmay be taken from a second location that is proximal to the stenoticlesion. In some such embodiments, the first set of pressure informationcan include information regarding pressure drop across the stenoticlesion. In some embodiments, the processor may be further adapted toreceive a second ultrasound signal representative of a secondintravascular physical dimension measurement taken near the stenoticlesion. In some embodiments, the processor may be further adapted toreceive a third ultrasound signal representative of a thirdintravascular physical dimension measurement taken near the stenoticlesion. In some embodiments, the processor may be adapted to receive thesecond ultrasound signal and/or the third ultrasound signalcontemporaneously with each other and/or with the first pressure signaland the first ultrasound signal. In some embodiments, the first set ofultrasound information may be based on the first intravascular physicaldimension measurement, the second intravascular physical dimensionmeasurement, and/or the third intravascular physical dimensionmeasurement. In some embodiments, the first set of ultrasoundinformation may include information regarding a diameter orcross-sectional profile of the vessel lumen adjacent the stenoticlesion. In some embodiments, the second intravascular physical dimensionmeasurement may be taken from a second location that is axially spacedin the vessel lumen from a first location at which the firstintravascular physical dimension measurement may be taken. In someembodiments, the control panel may be further adapted to receive fromthe processor a second set of ultrasound information based the secondintravascular physical dimension measurement. In some such embodiments,the control panel may be adapted to display the second set of ultrasoundinformation. In some instances, the first set of ultrasound informationmay include information regarding a first diameter or a firstcross-sectional profile of the vessel lumen at the first location, andthe second set of ultrasound information may include informationregarding a second diameter or a second cross-sectional profile of thevessel lumen at the second location.

BRIEF DESCRIPTION OF DRAWINGS

The details of one or more examples are set forth in the accompanyingdrawings and the description below. Other features, objects, andadvantages will be apparent from the description and drawings, and fromthe claims.

FIG. 1 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 2 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 3 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 4 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 5 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 6 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 7 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 8 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 9 is a perspective view of a vessel sensing system in accordancewith embodiments of the present invention.

FIG. 10A is an illustrative waveform of response signals from twoultrasound transducers with respect to time, with blood being theultrasound medium.

FIG. 10B is an illustrative waveform of response signals from twoultrasound transducers with respect to time, with a blood displacementfluid being the ultrasound medium.

FIG. 11A is an illustrative waveform of the frequency of a stimulussignal with respect to time for multiple ultrasound transducers.

FIG. 11B is an illustrative waveform of how three different ultrasoundtransducers respond to a varying stimulus frequency.

FIG. 11C is an illustrative waveform of the magnitude of a responsesignal coming from three different ultrasound transducers with respectto time.

FIG. 12A is an illustrative waveform of the magnitude of a responsesignal coming from three different ultrasound transducers with respectto time.

FIG. 12B is an end view of a patient's vessel with a vessel sensingsystem in accordance with embodiments of the present invention.

FIG. 13 is an illustrative waveform of the magnitude of a responsesignal coming from an ultrasound transducer ring with respect to time.

FIG. 14 is a schematic end view of an illustrative ultrasound transducerring used in connection with embodiments of the present invention.

FIG. 15 is a schematic end view of an illustrative ultrasound transducerring used in connection with embodiments of the present invention.

FIG. 16a is a schematic side view of a distal sheath with anillustrative ultrasound transducer ring used in connection withembodiments of the present invention.

FIG. 16b is a schematic end view of an illustrative ultrasound receiverring used in connection with embodiments of the present invention.

FIG. 16c is a schematic end view of an illustrative ultrasoundtransmitter ring used in connection with embodiments of the presentinvention.

DETAILED DESCRIPTION

The following detailed description is exemplary in nature and is notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the following description providespractical illustrations for implementing exemplary embodiments of thepresent invention. Examples of constructions, materials, dimensions, andmanufacturing processes may be provided for selected elements, and allother elements employ that which is known to those of skill in thefield. Those skilled in the art will recognize that many of the examplesprovided have suitable alternatives that can be utilized.

FIGS. 1-8 show various embodiments of a vessel sensing system 10. Thevessel wall 32 is cut away to show the interior of the vessel. Arrow Dpoints in the distal direction, meaning that the direction opposite thearrow D is the proximal direction or the direction that leads outside ofthe patient's body. As can be seen, FIGS. 1-8 show a stenotic lesion 36formed in the vessel wall 32.

Embodiments of the vessel sensing system 10 can identify at least twocharacteristics of the stenotic lesion 36 for purposes of determiningwhether intervening action should be taken. The vessel sensing system 10can include a pressure transducer 40 that can be used to determine howthe stenotic lesion 36 impacts the pressure of the blood as the bloodflows past the stenotic lesion 36. Additionally, embodiments of thevessel sensing system 10 can include an ultrasound transducer (e.g., theultrasound transducer ring 70 in FIGS. 1, 4 and 7 or the array ofindividual ultrasound transducers 71 in FIGS. 2, 3, 5, 6 and 8), whichcan determine, among other things, the interior diameter of the vessellumen adjacent the stenotic lesion 36 (and/or the cross-sectionalarea/profile for lesions with a non-circular profile) and the interiordiameter of the vessel itself. These characteristics—the pressure dropacross the stenotic lesion 36 and the interior diameter of the vessellumen adjacent the stenotic lesion 36—can provide valuable informationto inform a care provider's decision of whether to take interveningaction. In some embodiments, one or both of these characteristics can becombined with information provided by an angiogram to aid a careprovider in determining whether to have an angioplasty performed, have astent implanted, etc.

Pressure sensors that can be used in embodiments of the presentinvention can take a variety of forms. For example, in some embodiments,the pressure transducer 40 may be a fiber optic pressure sensor. Anexample of a fiber optic pressure sensor is a Fabry-Perot fiber opticpressure sensor, which is a commercially available sensor. Examples ofFabry-Perot fiber optic sensors are the “OPP-M” MEMS-based fiber opticpressure sensor (400 micron size) manufactured by Opsens (Quebec,Canada), and the “FOP-MIV” sensor (515 micron size) manufactured by FisoTechnologies, Inc. (Quebec, Canada). In embodiments of the inventionusing the Fabry-Perot fiber optic pressure sensor as the pressuretransducer 40, such a transducer works by having a reflective diaphragmthat varies a cavity length measurement according to the pressureagainst the diaphragm. Coherent light from a light source travels downthe fiber and crosses a small cavity at the sensor end. The reflectivediaphragm reflects a portion of the light signal back into the fiber.The reflected light travels back through the fiber to a detector at thelight source end of the fiber. The two light waves, the source light andreflected light travel in opposite directions and interfere with eachother. The interference pattern will vary depending on the cavitylength. The cavity length will change as the diaphragm deflects underpressure. The interference pattern is registered by a fringe patterndetector. In some embodiments, the pressure transducer 40 may be apiezo-resistive pressure sensor (e.g., a MEMS piezo-resistive pressuresensor). In some embodiments, the pressure transducer 40 may be acapacitive pressure sensor (e.g., a MEMS capacitive pressure sensor). Apressure sensing range from about −50 mm Hg to about +300 mm Hg(relative to atmospheric pressure) may be desired for making manyphysiological measurements with the pressure transducer 40.

In some embodiments, multiple pressure sensors can be spaced axially inthe vessel lumen from one another. For example, two, three, four, five,six or more pressure transducers may be spaced apart from one another byequal or unequal distances. In some embodiments, the distance betweenthe multiple pressure transducers may be variable. More detail in thisregard is provided elsewhere herein (see, e.g., FIG. 9 and thecorresponding discussion).

Ultrasound transducer(s) 70, 71 used in connection with embodiments ofthe vessel sensing system 10 can have a variety of characteristics.Commonly, ultrasound transducers comprise piezoelectric crystals thatdeform in response to electrical signals at predetermined frequencies.The frequency at which a crystal deforms depends on how the crystal ismanufactured. When the crystals deform at ultrasonic frequencies, theyemit ultrasound energy. In intravascular ultrasound applications, thecrystals are commonly positioned generally axially so that theultrasound energy propagates through the blood (or other fluid) in agenerally radial direction. The ultrasound energy is then partlyreflected back to the crystal, which is again deformed in a manner thatgenerates an electrical return signal that can be provided to processingequipment for processing. How the crystal is manufactured can alsoimpact the frequency at which the crystal can respond. Higher frequencyultrasound energy (e.g., greater than 50 MHz) can provide resolutionthat is very good, but differentiation between the blood (or otherfluid) and the vessel wall 32 is not as good. In contrast, lowerfrequency ultrasound energy can provide differentiation that is verygood but resolution that is not as good. The ultrasound transducer canbe an ultrasound transducer ring 70 that emits ultrasound energy roughlyuniformly in all radial directions. In some embodiments, multipleindividual ultrasound transducers 71 may be arranged to form a ring soas to emit ultrasound energy in specific radial directions. For example,in some embodiments three individual ultrasound transducers 71 may bespaced evenly about a circumference, thereby emitting ultrasound energyin radial directions 120 degrees spaced apart from each other. Larger orsmaller numbers of individual ultrasound transducers 71 (e.g., 2, 3, 4,5, 6, 7, or more) may be used, and the spacing between them may be evenor uneven. In another example, multiple individual ultrasoundtransducers 71 may be spaced about a circumference and the phase of thesignal may be controlled in order to focus the resulting ultrasonicwave. The focusing position can be varied substantially continuously inorder to discern the peak.

Determining the diameter or cross-sectional area/profile of the vessellumen adjacent a stenotic lesion can be valuable for characterizing thelesion. In some instances, the diameter or cross-sectional area/profilecan be used to assess how much impact the stenotic lesion has on thepatient's physiology. In some instances, the diameter or cross-sectionalarea/profile can be used to correct errors in FFR calculations based onobjects being in the vessel lumen adjacent the lesion. In someinstances, the diameter or cross-sectional area/profile can be used tochoose an appropriate stent with more confidence than if the diameter orcross-sectional area/profile had been estimated via an angiogram. Insome instances, the diameter or cross-sectional area/profile can be usedafter stent deployment to determine whether the stent is fully deployed.

In some embodiments, transducers for measuring other physiologicalparameters of a patient can be used. For example, some embodimentsincorporate a transducer for measuring a blood parameter, such as bloodtemperature, blood pH, blood oxygen saturation levels, and so on. Thetransducer may be configured to then generate a signal representative ofthe physiological parameter. Such transducer(s) may be used tosupplement the pressure transducer(s) and/or the ultrasoundtransducer(s), or such transducer(s) may be used in place of thepressure transducer(s) and/or the ultrasound transducer(s). Informationprovided by such transducer(s) can be used to further characterize astenotic lesion and/or for other purposes.

Embodiments of the vessel sensing system 10 include specific structurefor delivering the ultrasound transducer(s) 70, 71 and the pressuretransducer 40 to the stenotic lesion 36. In some embodiments, thatspecific structure includes a distal sleeve 20 coupled to a proximalportion 50. The distal sleeve 20 can include a guidewire lumen 22through which a guidewire 30 may pass. In this way, a guidewire 30 mayfirst be delivered to the area of interest (e.g., an area that includesthe stenotic lesion) and the proximal end of the guidewire 30 (i.e., theend that is outside of the patient's body) may be inserted into theguidewire lumen 22 of the distal sleeve 20 such that the distal sleeve20 may be guided along the guidewire 30 to the area of interest. Withthe proximal portion being coupled to the distal sleeve 20, the proximalportion 50 may likewise be delivered to the area of interest via theguidewire 30.

In FIGS. 1-9, conductor 60 is shown as being connected to pressuretransducer 40, and various conductors 80, 81, 82 are shown as beingconnected to ultrasound transducers 70, 71. Examples of conductorsinclude coaxial cable, twisted pair cable, etc. Electrical signals, asdiscussed elsewhere herein, are transmitted to and from the transducersvia the respective conductors. As shown, the conductors 60, 80, 81, 82extend within one or more lumens of the proximal portion 50. Inpractice, the conductors 60, 80, 81, 82 are typically not exposed to theblood (or blood displacement fluid) flowing through the vessel lumen. Insome configurations, a cover can be wrapped around distal sheath 20 toisolate the conductors 60, 80, 81, 82 from the vessel lumen. In someconfigurations, one or more conductors 60, 80, 81, 82 may be embeddedinto the distal sheath 20. Electrical impedance of the conductors 60,80, 81, 82 can be designed/selected to match that of the respectivetransducer 40, 70, 71 (typically between 10 ohms and 100 ohms). In someinstances, the conductors 60, 80, 81, 82 may be designed/selected tominimize loss of the electrical signal travels to and from therespective transducers 40, 70, 71 (e.g., 1-2 dB). In many instances, thediameter of each of the conductors 60, 80, 81, 82 may be minimized (inthe context of other design constraints) to minimize any degradation ofcatheter deliverability due to added stiffness of any of the conductors60, 80, 81, 82.

As can be seen, the axial length of the distal sleeve 20 is relativelysmall in comparison with the length of the guidewire 30, which extendsproximally from the area of interest that includes the stenotic lesion36 all the way back proximally out of the patient's body. This canprovide significant advantages over catheters that extend over theguidewire 30 from outside of the patient's body all the way into thearea of interest. For example, once the guidewire 30 has been advancedall the way into the area of interest, it can be quite beneficial toleave it there and not retract it until dictated by the medicalprocedure. On the other hand, it may be desirable to introduce thevessel sensing system 10 into the patient's vessel, take relevantmeasurements, remove the vessel sensing system 10, and use the guidewire30 for other purposes (e.g., delivering a stent to the stenotic lesion36). If the pressure transducer 40 and the ultrasound transducer(s) 70,71 were delivered by a catheter that extended from the area of interestall the way outside of the patient's body, it would be very difficult toremove that catheter from the patient's body while maintaining theposition of the guidewire 30. In contrast, a vessel sensing system 10with a distal sleeve 20 having a relatively short axial length may beremoved from the patient's body while holding the guidewire 30 in place.Additional detail about the advantages of using such a distal sleeve 20can be found in commonly assigned U.S. patent application Ser. No.12/557,685 (“Physiological Sensor Delivery Device and Method”), which ishereby incorporated by reference herein in its entirety.

The pressure transducer 40 and the ultrasound transducer(s) 70, 71 canbe positioned in various locations in vessel sensing system 10. FIGS. 1,2 and 3 show the ultrasound transducer(s) 70, 71 coupled to the distalsleeve 20 distal of the pressure transducer 40. FIGS. 4, 5 and 6 showthe ultrasound transducer(s) 70, 71 coupled to the distal sleeve 20proximal of the pressure transducer 40. FIGS. 7 and 8 show theultrasound transducer(s) 70, 71 coupled to the proximal portion 50.While the figures show the pressure transducer 40 coupled to the distalsleeve 20 in a similar location, the pressure transducer 40 may belocated more proximal or more distal on the distal sleeve 20 or on theproximal portion 50. In some embodiments, the pressure transducer 40and/or the ultrasound transducer(s) 70, 71 can be spaced in variouspositions about the circumference of the distal sleeve 20 and/or theproximal portion 50. As noted elsewhere herein, multiple pressuretransducers can be provided—spaced axially in the vessel lumen from oneanother and/or about the circumference of the distal sleeve 20 and/orthe proximal portion 50. In some embodiments, multiple ultrasoundtransducers (and/or sets of ultrasound transducers) may be spacedaxially in the vessel lumen apart from one another along the distalsleeve 20 and/or the proximal portion 50. Many other variations arecontemplated, depending on the particular application.

In use, the pressure transducer 40 can be used to measure the pressuredrop across the stenotic lesion 36. A technique for evaluating thedegree to which a stenotic lesion 36 obstructs flow through a bloodvessel is called the Fractional Flow Reserve measurement (FFR). Tocalculate the FFR for a given stenotic lesion, two blood pressurereadings are taken—one on the distal side of the stenosis (e.g.,downstream from the stenosis), the other pressure reading is taken onthe proximal side of the stenosis (e.g., upstream from the stenosis,towards the aorta). The FFR is defined as the ratio of maximal bloodflow in a stenotic artery, taken distal to the lesion, to normal maximalflow, and is typically calculated based on a measured pressure gradientof the distal pressure (less the venous pressure) to the proximalpressure (less the venous pressure). The FFR is therefore a unitlessratio of the distal and proximal pressures. The pressure gradient, orpressure drop, across a stenotic lesion is an indicator of the severityof the stenosis, and the FFR is a useful tool in assessing the pressuredrop. The more restrictive the stenosis is, the greater the pressuredrop, and the lower the resulting FFR. The FFR measurement may be auseful diagnostic tool. For example, clinical studies have shown that anFFR of less than about 0.75 may be a useful criterion on which to basecertain therapy decisions. Pijls, DeBruyne et al., Measurement ofFractional Flow Reserve to Assess the Functional Severity ofCoronary-Artery Stenoses, 334: 1703-1708, New England Journal ofMedicine, Jun. 27, 1996. A physician might decide, for example, toperform an interventional procedure (e.g., angioplasty or stentplacement) when the FFR for a given stenotic lesion is below 0.75, andmay decide to forego such treatment for lesions where the FFR is above0.75. More detail regarding FFR can be found in commonly assigned U.S.patent application Ser. No. 12/557,685 (“Physiological Sensor DeliveryDevice and Method”) which is incorporated by reference above.

In some instances, FFR can be adjusted to account for the presence ofdelivery equipment in the vessel lumen adjacent the stenotic lesion 36.For example, when the distal sleeve 20 carries the pressure transducer40 past the stenotic lesion 36 to a distal position, part of the distalsleeve 20 itself may remain in the narrowed vessel lumen defined by thestenotic lesion 36. This may introduce error due to the cross sectionalsize of the distal sleeve 20 and the guidewire 30. As the distal sleeve20 and the guidewire 30 cross the lesion, they introduce blockage, inaddition to that caused by the lesion itself. The measured distalpressure would therefore be somewhat lower than it would be without theadditional flow obstruction, which may exaggerate the measured pressuregradient across the lesion. Methods of correcting for such error aretaught in commonly assigned U.S. patent application Ser. No. 13/469,485(“Intravascular Sensing Method and System”), which is herebyincorporated by reference herein in its entirety. In some embodiments,additional information regarding the stenotic lesion 36 gathered throughmeans discussed herein may be used to enhance correction of FFR error.

In many instances, pressure measurements used for purposes ofcalculating a patient's FFR are taken when the patient is underhyperemic conditions. To cause the hyperemic conditions in the patient,adenosine (or other vasodilatory drug) is commonly administered to thepatient. The adenosine gets into the patient's downstream circulationand causes vasodilation, opening up the downstream vessels. This canminimize the variability in the downstream resistance to blood flow,thereby making the FFR ratio more representative of the pressure dropcaused by the stenotic lesion. Minimizing the variability in thedownstream blood flow can also have the effect of “standardizing” FFRratios, making them more readily comparable with other FFR ratios takenunder hyperemic conditions.

In some instances, administering a vasodilatory drug like adenosine to apatient can have drawbacks. It can add a significant amount of extrasetup time, which can have a detrimental effect on efficiency. In someinstances, vasodilatory drugs can cause discomfort to some patients. Forthese and other reasons, some care providers prefer to avoidadministering vasodilatory drugs to patients when assessing the severityof stenotic lesions.

A recent study proposed a method of measuring pressure drop across astenotic lesion without using vasodilatory drugs. This method, calledthe instantaneous wave-Free Ratio (iFR), relies on a short segment ofthe coronary waveform in which the downstream resistance to blood flowis relatively stable. The proximal and distal values on that segment ofthe coronary waveform are compared to one another to form a ratio that,like FFR, provides information regarding the pressure drop across thestenosis, which can aid care providers in deciding whetherinterventional action (e.g., a stent or angioplasty) is warranted.

FIG. 9 shows a vessel sensing system 10 with multiple pressuretransducers 40, 41 spaced axially from one another in the vessel lumen.In some embodiments, the pressure transducers 40, 41 can be positionedboth on the proximal portion 50, both on the distal sleeve 20, one onthe proximal portion 50 and one on the distal sleeve 20, and so on.Embodiments with multiple pressure transducers 40, 41 can beadvantageous in measuring both FFR and iFR. In both FFR and iFR, apressure transducer 40 can be positioned distal to the stenotic lesion36 and can provide distal pressure measurements to processing equipmentvia a pressure transducer conductor 60. For measuring pressure proximalto the stenotic lesion 36, a second pressure transducer 41 can bepositioned proximal to the stenotic lesion 36 and can provide proximalpressure measurements to processing equipment via a pressure transducerconductor. In some instances, proximal pressure may be measured moreaccurately and reliably via an invasive pressure transducer, like thesecond pressure transducer 41, than via an external pressure transducerthat measures proximal pressure through the fluid within a guidecatheter physically coupled to the external pressure transducer. This isbecause the shape of the waveform can be influenced by “ringing” and“damping” effects of the guide catheter, the fluid within the guidecatheter, and the external transducer. The increased accuracy andreliability provided by an invasive pressure transducer can beespecially beneficial for procedures that do not involve vasodilatorydrugs (e.g., iFR) because they are typically based on a pressure valuetaken at a particular segment of the coronary waveform, whereas FFRtypically uses only the mean proximal pressure.

Referring again to FIGS. 1-9, the ultrasound transducer(s) 70, 71 can beused to determine the interior diameter (or cross-sectional area, e.g.,for non-circular stenotic lesions) of the vessel lumen adjacent thestenotic lesion 36. In some embodiments, the ultrasound transducer(s)70, 71 can be used to determine the interior diameter across the entireaxial profile of the stenotic lesion 36. The ultrasound transducer(s)70, 71 can determine the interior diameter of the vessel lumen adjacentthe stenotic lesion 36 across the lesion's entire axial profile byemitting and receiving ultrasound energy as they are moved axially inthe vessel lumen from one side of the stenotic lesion 36 to the other.In some embodiments, the proximal portion 50, and thus the distal sleeve20, may be rotated (e.g., manually) during translation of the ultrasoundtransducer(s) 70, 71 across the lesion's axial profile (e.g., duringpullback of the proximal portion 50). In some such embodiments, therotational position can be correlated with the ultrasound signalsemitted/received. Some such embodiments can be used to providedimensional information at a variety of rotational positions, which canlead to an effective characterization of the vessel lumen adjacent thestenotic lesion 36. The ultrasound transducer(s) 70, 71 can bemanufactured to emit ultrasound energy in response to a stimulus signalat a predetermined frequency. The type of ultrasound energy emitted bythe ultrasound transducer(s) 70, 71 can be calibrated to clearlydifferentiate between fluid flowing in the vessel (e.g., blood, a blooddisplacement fluid such as saline, etc.) and the vessel wall 32.Ultrasound energy emitted at higher frequencies provides greaterresolution but less differentiation between the vessel fluid and thevessel wall 32, whereas ultrasound energy emitted at lower frequenciesprovides better differentiation between vessel fluid and vessel wall 32but not as good resolution. In many instances, when desiring theinterior diameter of the vessel lumen adjacent the stenotic lesion 36and not an entire image of the stenotic lesion 36, strongdifferentiation can be of more importance than high resolution.Embodiments in which the pressure transducer(s) 40, 41 comprise a fiberoptic sensor may be advantageous in that high frequency ultrasoundenergy and/or RF electrical noise can have minimal effect on theoperation of the fiber optic sensors.

In some instances, it may be advantageous to compare interior diametercalculations obtained by propagating ultrasound energy through a firstfluid with interior diameter calculations obtained by propagatingultrasound energy through a second fluid. For example, a first set ofinterior diameter calculations can be obtained by propagating ultrasoundenergy through blood flowing through the patient's vessel, and a secondset of interior diameter calculations can be obtained by propagatingultrasound energy through a blood displacement fluid (e.g., saline)flowing through the patient's vessel. The first and second sets ofinterior diameter calculations can be compared to one another to obtainmore reliable measurements. FIGS. 10A-10B provide illustrativewaveforms, with FIG. 10A showing the response signal through blood andFIG. 10B showing the response signal through a blood displacement fluid.The first peak in each response signal, T1B and T1S, can correspond tothe inner wall of the lesion, and the second peak in each responsesignal, T2B and T2S, can correspond to the vessel's outer wall. Thedifference between T1B and T0 will not match the difference between T1Sand T0 because ultrasound energy travels at different rates between thetwo fluids. On the other hand, the difference between T2B and T1B shouldmatch the difference between T2S and T1S because the ultrasound energyis reflecting from the lesion and vessel wall during both time periods.This relationship can make it easier to identify the first peak, whichcan then be used to determine the distance between the ultrasoundtransmitter and the inner wall and the lesion.

Referring again to FIGS. 1-9, in embodiments that use an ultrasoundtransducer ring 70, a single stimulus signal can be provided to theultrasound transducer ring 70 by way of a single ultrasound transducerconductor 80. The ultrasound transducer ring 70 can emit ultrasoundenergy roughly uniformly in all radial directions. The ultrasoundtransducer ring 70 can create an electrical signal based on theultrasound energy reflected back to it and can transmit that electricalsignal through ultrasound transducer conductor 80. That electricalsignal can then be used to determine the interior diameter of the vessellumen adjacent the stenotic lesion 36. The process of transmitting andreceiving ultrasound energy by the ultrasound transducer ring 70 can beperformed multiple times at multiple points as the ultrasound transducerring 70 is moved axially in the vessel lumen across the stenotic lesion36. Similarly, the individual ultrasound transducers 71 can receive astimulus signal either from a common conductor 81 or from separateindividual conductors 82. In some embodiments, the individual ultrasoundtransducers 71 may be configured to begin emitting ultrasound energyupon receiving a stimulus signal of approximately the same frequency. Insome embodiments, the individual ultrasound transducers 71 may beconfigured to begin emitting ultrasound energy in response to stimulussignals at different frequencies. For example, a stimulus frequency maybe varied over time causing (a) a first ultrasound transducer 71 tobegin emitting ultrasound energy at a first time and a first frequency,(b) a second ultrasound transducer 71 to begin emitting ultrasoundenergy at a second time and a second frequency, and (c) a thirdultrasound transducer 71 to begin emitting ultrasound energy at a thirdtime and a third frequency. In some embodiments, multiple individualultrasound transducers may be electrically tied together (e.g., a singlecoaxial conductor connecting with three ultrasound transducers). In somesuch embodiments, a very broadband signal (e.g., a short-time pulse or abroadband chirp) can be provided as a stimulus signal, which can exciteonly those frequencies to which the individual ultrasound transducersare sensitive. When the individual ultrasound transducers 71 receiveultrasound energy, they convert the received ultrasound energy to anelectrical signal and transmit the electrical signals via the commonconductor 81 or the individual conductors 82, depending on theparticular embodiment.

FIGS. 14, 15, and 16 a-16 b provide illustrative ultrasound transducerring embodiments. FIG. 14 shows an ultrasound transducer ring 70 withring transducer elements 70 a, 70 b, 70 c, which may operate at anominal center frequency between 10 MHz and 80 MHz, more typicallybetween 20 MHz and 60 MHz. The ring transducer elements 70 a, 70 b, 70 cmay be mechanically separated by kerfs 72 to inhibit mechanicalcross-talk between the ring transducer elements 70 a, 70 b, 70 c. FIG.15 shows a segmented ring transducer 70′ that includes three transducerelements 70′a, 70′b, 70′c. The size of the segmented ring transducerelements 70′a, 70′b, 70′c may be optimized to balance sensitivity andspatial resolution, which may depend in part on transducer aperturesize. In some embodiments, the transducer elements 70′a, 70′b, 70′c mayoperate at a nominal center frequency between 10 MHz and 80 MHz, moretypically between 20 MHz and 60 MHz. In some embodiments, each of thetransducer elements 70′a, 70′b, 70′c may operate at different nominalcenter frequencies between 10 MHz and 80 MHz, more typically between 20MHz and 60 MHz. An advantage of segmented ring transducer elements 70′a,70′b, 70′c operating at different frequencies is the ability to detectonly specific signal frequencies which may in turn facilitate physicaldimension measurements. The transducer ring 70 and segmented ringtransducer 70′ of FIGS. 14 and 15, respectively, may operator as both atransmitter and a receiver. FIG. 16a shows still another embodiment ofan ultrasound transducer 70″ that includes a separate transmitter 70″tand receiver 70″r. FIG. 16c shows a single-element ring transducer 70″tthat may operate at a nominal center frequency between 10 MHz and 80MHz, more typically between 20 MHz and 60 MHz. FIG. 16b shows a ringtransducer 70″r that includes three transducer elements 70″ra, 70″rb,70″rc. The transducer 70″ of FIGS. 16a, 16b, 16c that includes aseparate transmitter 70″t and receiver 70″r may enable a simplerultrasound transmitter while preserving improved spatial resolution of amultiple element receiver transducer.

The relative locations of the ultrasound transducer(s) 70, 71 and thepressure transducer 40 can impact the accuracy of the interior diameterand pressure drop measurements. In many embodiments, pressure drop ismeasured by positioning the pressure transducer 40 distal of thestenotic lesion 36. Proximal pressure can be measured either by fluidpressure taken proximal of the vessel sensing system 10 (e.g., aorticpressure) or by a second pressure transducer coupled, for example, tothe proximal portion 50 (see FIG. 9). Measuring pressure distal of thestenotic lesion 36 can be impacted by other objects within the vessellumen adjacent the stenotic lesion 36 such as the distal sleeve 20, theproximal portion 50, etc. It can be desirable to avoid positioning theultrasound transducer 70, 71 within the stenotic lesion 36 while thepressure transducer 40 is measuring pressure distal of the stenoticlesion 36. Thus, embodiments in which the ultrasound transducer(s) 70,71 are positioned distal to the pressure transducer 40 (e.g., FIGS. 1-3)may result in fewer objects being in the vessel lumen adjacent thestenotic lesion 36 during measurement of distal pressure, therebyreducing the error caused by having objects within the vessel lumenadjacent the stenotic lesion 36. In some instances, the vessel diameterdistal to the stenotic lesion 36 may decrease substantially in a shortdistance. In such instances, having the ultrasound transducer(s) 70, 71positioned distal to the pressure transducer 40 may impede the distalsleeve 20 from moving far enough distally to properly position thepressure transducer 40. In such cases, having the ultrasoundtransducer(s) 70, 71 positioned proximal to the pressure transducer 40may be desirable (though moving the ultrasound transducer(s) 70, 71completely across the stenotic lesion 36 may likewise be impeded by thedistal pressure transducer 40). In many embodiments, it may be desirableto position the ultrasound transducer(s) 70, 71 relatively close axiallyto the pressure transducer 40.

The desire to keep the vessel lumen adjacent the stenotic lesion 36relatively free from objects when measuring distal pressure may alsoimpact whether individual conductors 82 or a common conductor 81 areused to connect to the individual ultrasound transducers 71. Eachultrasound conductor 81, 82 can include a stimulus lead and a referenceor ground lead. If there are three individual ultrasound transducers 71positioned about the circumference of the distal sleeve 20, and eachindividual ultrasound transducer 71 is connected to a common ultrasoundconductor 81, that would result in six leads (two per individualultrasound transducer 71). This volume within the vessel lumen adjacentthe stenotic lesion 36 may or may not introduce too much error into thepressure drop measurement, depending on the size of the leads, the sizeof the vessel, the size of the stenotic lesion 36, and other factors.

FIGS. 11A-11C illustrate an embodiment having three individualultrasound transducers each configured to emit ultrasound energy atdifferent stimulus frequencies. As the stimulus signal is varied (FIG.11A), the time at which the stimulus signal frequency triggers each ofthe three individual ultrasound transducers may be recorded. Inanalyzing the response signal (FIG. 11B), it may be assumed that thefirst peak corresponds to the first transducer to have been triggered,the second peak corresponds to the second transducer to have beentriggered, and the third peak corresponds to the third transducer tohave been triggered. The peaks may signify that the ultrasound energyhas reflected off of the vessel wall rather than the fluid flowingthrough the vessel. The radial distance between each ultrasoundtransducer and the vessel wall can be based on the time that elapsesbetween when it is triggered and when its first peak response signal isreceived, along with the respective radial positions of the ultrasoundtransducers. That radial distance can be based on properties of thefluid flowing through the vessel (e.g., how fast ultrasound energytravels through the fluid). Many calculations of distance account forultrasonic dispersion effects.

FIGS. 12A-12B illustrate an embodiment having three individualultrasound transducers each configured to emit ultrasound energy atroughly the same stimulus frequency. FIG. 12B shows a vessel sensingsystem 210 that carries three individual ultrasound transducers 271 andis positioned within a vessel 232. In some embodiments, the responsesignal(s) may be analyzed to estimate an average interior diameter ofthe vessel 232. For example,D _(avg)=⅔(D ₁ +D ₂ +D ₃)+D _(vss)and⅔(D ₁ +D ₂ +D ₃) is proportional to ⅔(T ₁ +T ₂ +T ₃)where D_(avg) is the average interior diameter of the relevant axiallocation; D₁, D₂, and D₃ are the distances calculated based on theresponse signals from each ultrasound transducer 271; D_(vss) is thediameter of the vessel sensing system that carries the three individualultrasound transducers 271; and T₁, T₂, and T₃ are times to the peaks inthe return signal. In some instances, a vessel lumen can be modeled ashaving a circular cross-sectional profile, but it should be understoodthat vessel lumens can have a variety of cross-sectional profiles.

FIG. 13 illustrates an embodiment having an ultrasound transducer ringthat emits ultrasound energy radially in a generally uniform manner. Insome embodiments, a weighted center WC under the response signal curvemay be determined according to known methods. The time T_(WC) thatcorresponds to the weighted center WC can be used to estimate theaverage distance from the ultrasound transducer ring to the lesion atthe associated axial location. When such a waveform is relativelynarrow, it may be inferred that the ultrasound transducer ring isroughly centered within the patient's vessel. When such a waveform isrelatively broad, it may be inferred that the ultrasound transducer ringis not centered within the patient's vessel.

In the foregoing detailed description, the invention has been describedwith reference to specific embodiments. However, it may be appreciatedthat various modifications and changes can be made without departingfrom the scope of the invention. Thus, some of the features of preferredembodiments described herein are not necessarily included in preferredembodiments of the invention which are intended for alternative uses.

The invention claimed is:
 1. An intravascular transducer delivery devicecomprising: a distal sleeve having a guidewire lumen for slidablyreceiving a medical guidewire; a proximal portion coupled to the distalsleeve; and an ultrasound transducer coupled to the distal sleeve and/orthe proximal portion, the ultrasound transducer comprising: anultrasound ring transmitter; and an ultrasound ring receiver adjacentthe ultrasound ring transmitter, wherein the ultrasound ring receiverincludes first, second, and third receiver elements positioned about acircumference of the distal sleeve and/or the proximal portion.
 2. Theintravascular transducer delivery device of claim 1, wherein the firstreceiver element, the second receiver element, and the third receiverelement are coupled to the distal sleeve.
 3. The intravasculartransducer delivery device of claim 1, wherein the first receiverelement, the second receiver element, and the third receiver element arecoupled to the distal sleeve.
 4. The intravascular transducer deliverydevice of claim 1, further comprising a first pressure transducercoupled to the distal sleeve and/or the proximal portion, the firstpressure transducer adapted to take a first intravascular fluid pressuremeasurement and generate a first pressure signal representative of thefirst intravascular fluid pressure measurement.
 5. The intravasculartransducer delivery device of claim 4, wherein the first pressuretransducer is a fiber optic pressure transducer.
 6. The intravasculartransducer delivery device of claim 4, further comprising: (i) a secondpressure transducer coupled to the distal sleeve and/or the proximalportion, the second pressure transducer adapted to take a secondintravascular fluid pressure measurement and generate a second pressuresignal representative of the second intravascular fluid pressuremeasurement, wherein the second pressure transducer is spacedlongitudinally from the first pressure transducer by a distance thatcorresponds to a stenotic lesion.
 7. The intravascular transducerdelivery device of claim 4, wherein the first receiver element, thesecond receiver element, and the third receiver element are positioneddistal to the first pressure transducer.
 8. The intravascular transducerdelivery device of claim 1, further comprising one or more transducerconductors in communication with the ultrasound transducer, wherein theone or more transducer conductors are configured to provide a stimulussignal to the ultrasound ring transmitter, and wherein the one or moretransducer conductors are adapted to communicate a first ultrasoundsignal received at the first receiver element, a second ultrasoundsignal received at the second receiver element, and a third ultrasoundsignal received at the third receiver element, outside of a patientthrough the proximal portion.
 9. The intravascular transducer deliverydevice of claim 1, wherein the one or more transducer conductorscomprise a single ultrasound transducer conductor configured to providethe stimulus signal at respective distinct frequencies to the firstultrasound transducer, the second ultrasound transducer, and the thirdultrasound transducer and adapted to communicate the first ultrasoundsignal, the second ultrasound signal, and the third ultrasound signaloutside of the patient through the proximal portion.
 10. Theintravascular transducer delivery device of claim 8, wherein the firstultrasound signal, the second ultrasound signal, and the thirdultrasound signal each comprise distinct frequencies from one anotherbased on respective distinct frequencies of the provided stimulussignal; wherein the first ultrasound signal is representative of a firstintravascular distance value, the second ultrasound signal isrepresentative of a second intravascular distance value, and the thirdultrasound signal is representative of a third intravascular distancevalue.
 11. The intravascular transducer delivery device of claim 10,wherein the first intravascular distance value, the second intravasculardistance value, and the third intravascular distance value each comprisea radial distance from the first receiver element, the second receiverelement, and the third receiver element to a vessel or lesion wall,respectively.